Mapping Mountains – Hill Reclassifications – 200m Twmpau

Pt. 252.3m (SH 697 167) – 200m Sub-Twmpau addition

There has been an addition to the 200m Twmpau list due to LIDAR analysis conducted by Myrddyn Phillips, with the criteria for this list being:

200m Twmpau - Welsh hills at and above 200m and below 300m in height with 30m minimum drop, with an accompanying sub list entitled the 200m Sub-Twmpau with the criteria for this sub category being all Welsh hills at and above 200m and below 300m in height with 20m and more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.

Prior to LIDAR analysis this hill was listed with c 19m of drop based on the 252m summit spot height that appears on the Ordnance Survey Interactive Coverage Map hosted on the Geograph website and an estimated bwlch height of c 233m based on bwlch contouring between 230m – 240m.

Extract from the Ordnance Survey Interactive Coverage Map hosted on the Geograph website

As the name of the ffridd taking in this hill’s summit has not been confirmed the hill is being listed by the point (Pt. 252.3m) notation and it is adjoined to the Cadair Idris group of hills, which are situated in the south-western part of North Wales (Region A, Sub-Region A3), and the hill is positioned with the A 493 road to its north and has the town of Dolgellau towards its east north-east.

As the hill is a part of designated open access land the summit can be approached from a number of directions, with a bridleway to the south of the hill probably giving easiest access.

The addition of this hill to 200m Sub-Twmpau status is due to LIDAR analysis conducted by Myrddyn Phillips.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

The 1m DTM LIDAR analysis gives the hill the following details:

Name:  Pt. 252.3m

Summit Height:  252.3m

Summit Grid Reference:  SH 69722 16736

Bwlch Height:  232.05m

Bwlch Grid Reference:  SH 69739 16620 & SH 69730 16624 & SH 69732 16628

Drop:  20.2m

LIDAR image of Pt. 252.3m

Therefore, the 252.3m LIDAR analysis for the summit position at SH 69722 16736 and the 232.05m LIDAR analysis for the bwlch position at SH 69739 16620 and SH 69730 16624 and SH 69732 16628 gives this hill 20.2m of drop, which confirms its addition to 200m Sub-Twmpau status.

The full details for the hill are:

Group:  Cadair Idris

Name:  Pt. 252.3m

OS 1:50,000 map:  124

Summit Height:  252.3m (LIDAR)

Summit Grid Reference:  SH 69722 16736 (LIDAR)

Bwlch Height:  232.05m (LIDAR)

Bwlch Grid Reference:  SH 69739 16620 & SH 69730 16624 & SH 69732 16628 (LIDAR)

Drop:  20.2m (LIDAR)

Myrddyn Phillips (June 2018)